Many portable communication devices such as selective call receivers, e.g. pagers, typically alert a user upon the occurrence of one of a number of possible events. The alert typically can be one of a visual, an audible or a tactile alert, or a combination thereof. The tactile alert normally provides a silent alert signal to the user. These alerting functions are well known in the art.
Conventional vibratory alerting devices (e.g., tactile alerting devices), such as shown in FIG. 1, have employed a vibrator motor 100, typically a dc motor, comprising a cylindrical housing 102 having a rotating shaft 104 attached to an external unbalanced counterweight 106 to provide the "silent" tactile alert. The cylindrical body 102 normally is held in place on a printed circuit board 108 by motor bracket 110. With this configuration, a dc current can be selectively applied to the vibrator motor 100 to consequently provide the tactile alert to the user.
A number of significant drawbacks have become evident with this conventional tactile alerting configuration. First, substantial size and bulk are added to the communication device, which is contrary to the current trend towards miniaturization in modern receiver designs. Second, the conventional vibrator motor 100 requires additional assembly time and post soldering operations, which significantly increases manufacturing costs. Third, subsequent repair costs are seriously affected by the required soldering/de-soldering of the vibrator motor 100, again adding costs to the product. Fourth, the required handling and the number of moving parts significantly increase the number of opportunities for introducing defects, both during manufacturing and during servicing, thereby degrading the overall quality of the product as perceived by the user. Lastly, the printed circuit board 108, which is typically flexible, tends to dampen the vibrating motion that is delivered to the housing and ultimately felt by the user as the tactile alert. Hence, the conventional vibrator motor 100 mounted on the printed circuit board 108 is inherently inefficient at delivering vibratory motion to the user, while significantly increasing the costs of the product and reducing the overall quality.
U.S. Pat. No. 4,728,837, issued to Krishna Bhadra on Mar. 1, 1988, shows a vibration generator useful for vibratory screening machinery. The construction and arrangement of the elements are typically directed toward vibrating processes such as vibratory screens. The size, bulk, and arrangement of the electromagnets, however, normally prohibits use of the vibration generator in a portable communication device such as a selective call receiver. Further, increased manufacturing costs, increased subsequent repair costs, and degraded quality as perceived by the user may be incurred due to the required number of parts and the number of assembly/disassembly steps.
Accordingly, there exists a need in the art for an improved vibratory alerting device.